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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 4 |
| 4 | 13 |
| 5 | 25 |
| 6 | 72 |
| 7 | 166 |
| 8 | 450 |
| 9 | 1124 |
| 10 | 2973 |
| 11 | 7603 |
| 12 | 19865 |
| 13 | 51199 |
| 14 | 132982 |
| 15 | 343290 |
| 16 | 888309 |
| 17 | 2292325 |
| 18 | 5918742 |
| 19 | 15258937 |
| 20 | 39329418 |
[1,3,4,13,25,72,166,450,1124,2973,7603,19865, 51199,132982,343290,888309,2292325,5918742, 15258937,39329418] |